极冠，汉语拼音jí guān ㄐㄧˊ ㄍㄨㄢ，指的是火星两极附近白色明亮的部分。
每到冬季，火星的极冠被一层薄薄的二氧化碳覆盖。
Every winter, Mars's polar cap is sheathed in a thin blanket of carbon dioxide.
火星的大气中有水蒸气，其北极极冠中有水冻冰块。
Mars has water vapour in its atmosphere, and water ice in the shining cap at its North Pole.
由于往往是通过天文望远镜的目镜拍摄，火星的方向是颠倒的，行星的北极冠在下面。
As often seen through an astronomical telescope eyepiece, the planet's orientation is inverted, with Mars' north polar cap at the bottom.
应用推荐